Yoke structure with a step

ABSTRACT

A planar top yoke in a magnetic write head is disclosed. The top yoke includes a backside region and a second pole tip region that is thinner than the backside region and forms a step at the ABS. Alternatively, a front section of the backside region includes a step with a thickness greater than the second pole tip region. Therefore, flux is directed from a thicker backside region toward the gap side of the second pole tip layer near the ABS. A lower flux density is formed at the top of the step at the ABS which reduces the flank field/gap field ratio and prevents unwanted erasure of adjacent data tracks. A high gap field is achieved while maintaining a low flank field during high write current conditions. The step recess from the ABS toward the backside region is about 0.2 to 2 microns.

This is a continuation of U.S. patent application Ser. No. 10/776,813,filed on Feb. 11, 2004 now U.S. Pat. No. 7,102,852, which is hereinincorporated by reference in its entirety, and assigned to a commonassignee.

FIELD OF THE INVENTION

The invention relates to a write head having a planar top yoke whichincludes a second pole tip region at the ABS that is thinner than thebackside region of the top yoke and in particular to a second pole tipregion with a step that controls the flux flow and reduces the leakagefield at the second pole tip.

BACKGROUND OF THE INVENTION

A magnetic disk drive includes a rotating magnetic disk with circulardata tracks and read and write heads that may form a merged head whichis attached to a slider on an arm that positions the head. During arecording operation, the merged head is suspended over the magnetic diskon an air bearing surface (ABS). The write head has first and secondpole pieces that are connected at a back gap region. The first andsecond pole pieces or yokes have first and second pole tips,respectively, that are separated by a write gap layer and terminate atthe ABS. An electric current is passed through coils formed around theback gap region to magnetize the first and second pole pieces. As theleading first pole tip is moved over a magnetic disk, a magnetic fluxpasses from the second pole tip onto a data track and then to the firstpole tip and is called the gap field.

A trend in the industry is to increase the recording density whichrequires increased coercivity to overcome the demagnetization field ofthe magnetic transition. However, as the data track width shrinks, thewrite head field strength tends to decrease due to saturation of thesecond pole tip region. Unfortunately, a high-end hard disk drive (HDD)generates such a high data rate transfer that not only is greater writehead field strength required, but a faster flux rise time is needed. Toproduce a large enough overwrite value, the write current is boosted anda large overshoot of its waveform results. This condition causes severeexcess saturation of the second pole tip and adjacent track erasuresoften occur.

A conventional planar write head 10 is depicted in FIG. 1 and features abottom yoke or first pole piece 2 formed on a substrate 1 which may beceramic, for example. There is a planar top yoke or second pole piece 3that is connected to the bottom yoke 2 through a back gap region 4 andwhich is covered by an overcoat layer 14. The bottom yoke 2 has apedestal 5 with a first pole tip 7 and a throat region 6. The top yoke 3has a second pole tip region 3 a that terminates at a second pole tip 8at the ABS. The throat region 6 and second pole tip region 3 a areseparated by a write gap layer 9 which is non-magnetic and extends fromthe ABS toward the back gap region 4 by a distance TH which is thethroat height. At this point, the bottom yoke 2 begins to separate fromthe top yoke 3 and forms a cavity with sidewalls and a bottom. Aconformal first dielectric layer 11 is formed on the sidewalls andbottom of the cavity. A coil layer 13 is wrapped between the top yoke 3and bottom yoke 2 and around the back gap region 4 and is contained in asecond dielectric layer 12 which is coplanar with the top of the writegap layer 9. This design enables the top yoke 3 to be formed on a planarsurface to allow good track width control for the second pole tip 8definition. In a merged head design, the bottom yoke 2 of the write headalso serves as the top layer of the read head (not shown).

Referring to FIG. 2, a top-down view of the write head 10 is depicted inwhich the overcoat layer 14 and dielectric layers 11, 12 have beenremoved to show the arrangement of the top yoke 3, bottom yoke 2, backgap region 4, and coil layer 13. The top yoke 3 has a length d₁ of about5 to 25 microns which includes the length d₂ of the second pole tipregion 3 a. The maximum width of the top yoke 3 and bottom yoke 2 is w₁.The main body of the top yoke 3 behind the second pole tip region 3 a isalso referred to as the back side region.

Referring to FIG. 3, a side view from the plane 15-15 in FIG. 1 is shownthat depicts the second pole tip region 3 a and the second pole tip 8 atthe ABS end of the top yoke. The write gap layer 9 overlays the firstpole tip 7 and the pedestal 5. The second dielectric layer 12 is oneither side of the write gap layer 9 and pedestal 5 at the ABS while thesecond pole tip region 3 a is surrounded on the top and sides by theovercoat layer 14.

In a conventional planar writer shown in FIG. 4 which is an enlargedview of the ABS end of write head 10 in FIG. 1, the top yoke 3 canprovide a significant amount of flux 16 toward the write gap layer 9.The flux 16 passes from the second pole tip region 3 a through thesecond pole tip 8 onto a recording track (not shown) and then throughthe first pole tip 7 and into pedestal 5. However, there is some leakagerepresented by a flank field 17 across the ABS onto an adjacentrecording track. When a high write current is employed with largeovershoot waveforms, then a significant amount of erasure on adjacentdata tracks occurs because of the flank field. Therefore, a new writehead design is needed that reduces the flank field to prevent unwanteddata track erasure.

In U.S. Pat. No. 6,473,276, a merged magnetic head which includes awrite head with a single sided notched first pole piece is described. Adata track is formed that has a narrow erase band on one side and a wideerase band on the other side. The narrow erase band enables a largesignal amplitude while a wide erase band allows flexibility in spacingthe read head from adjacent tracks.

A magnetic write head with a zero throat height (ZTH) layer is disclosedin U.S. Pat. No. 6,111,724. The ZTH is formed close to the first andsecond pole tips to reduce flux loss between the first and second polepieces. The method of forming the ZTH layer avoids reflective notchingand thereby improves definition of the second pole tip.

Another second pole piece is described in U.S. Pat. No. 6,337,783 wherea second yoke component is stitched to the back and sides of the topedge of a second pole tip to provide improved magnetic coupling. The topstitched area is minimized so that the coil layers may be closer to theABS to increase the data rate of the head. In related art disclosed inU.S. Pat. No. 6,029,339, the stitching of the yoke component to thesecond pole tip is achieved by a method that avoids reflective notchingin the top yoke.

Unwanted side writing is prevented in U.S. Pat. No. 6,504,675 bymodifying the second pole tip such that the leading edge of the pole tipis narrower than the trailing edge. Thus, the second pole tip has atrapezoidal cross-section with tapered sides.

SUMMARY OF THE INVENTION

One objective of the present invention is to provide a planar top yokein a write head that reduces the flank field at the ABS.

A further objective of the present invention is to provide a planar topyoke in accordance with the first objective that does not reduce the gapfield strength for writing a data track.

These objectives are achieved in a first embodiment with a write headwhich includes a top planar yoke comprised of second pole tip region anda backside region. The backside region has a front section adjacent tothe back end of the second pole tip region as viewed from the ABS plane.The front end of the second pole tip region is the second pole tipformed along the ABS. The top planar yoke is connected to a bottom yokethrough a back gap region. The bottom yoke has a pedestal with a shortthroat region and a first pole tip formed at the ABS. The throat regionand second pole tip region are separated by a write gap layer. In oneembodiment, the top of the write gap layer is coplanar with the top of acavity formed between the top and bottom yokes. The cavity has sidewallsand a bottom which is filled with a dielectric layer and extends fromthe throat region to the back gap region and beyond. Enclosed within thedielectric layer is a coil layer which surrounds the back gap region. Aninsulating overcoat layer is located on the planar top yoke.

The second pole tip region has a first thickness, a first width, twosides, a top and bottom, a back end that connects to the front end ofthe backside region, and a front end formed along the ABS. The backsideregion of the top yoke has a second thickness greater than the firstthickness, a top and bottom, and includes a front section adjacent tothe second pole tip region that flares outward and becomes wider withincreasing distance from the second pole tip region. A key feature isthat the top of the second pole tip region forms a step down toward theABS from the front section of the top yoke. The second pole tip regionhas a length of about 0.2 to 2 microns from the ABS to the front end ofthe backside region of the top yoke.

The bottoms of the second pole tip region and backside region arecoplanar with the top of the write gap layer. The sides of the secondpole tip region and backside region are perpendicular to the planecontaining the top surface of the write gap layer. This design causesthe magnetic flux from the backside region of the top yoke to passthrough the second pole tip region with a tilted angle toward the bottomor so-called gap side near the ABS. As a result, the flux isconcentrated on the gap side of the second pole tip region and a lowerflux density near the top of the second pole tip region minimizes themagnitude of the flank field.

In a second embodiment, the planar write head is comprised of the samecomponents as described in the first embodiment. The second pole tipregion has a first thickness, a first width, two sides, a top andbottom, a back end that connects to the front section of the backsideregion, and a front end or second pole tip formed along the ABS.However, the front section of the backside region is comprised of twosegments with different thicknesses that form a second step. A firstsegment of the front section has a second thickness greater than thefirst thickness, two sides, a top and bottom, a back end that connectsto the front end of a second segment, and a front end adjacent to theback end of the second pole tip region. The second segment of the frontsection has a third thickness greater than the second thickness andincludes two sides, a top and bottom, and a front end adjacent to theback end of the first segment. The second segment has the same thicknessas the main body of the top yoke in the backside region. The firstsegment represents a step down from the second segment toward the ABSand the second pole tip region is a step down from the first segmenttoward the ABS.

The bottoms of the first and second segments and the second pole tipregion are coplanar with the top surface of the write gap layer. Thesides of the first and second segments and of the second pole tip regionare perpendicular to the plane containing the top surface of the writegap layer. This design causes the magnetic flux from the backside regionof the top yoke to pass through the first and second segments of thefront section with a tilted angle toward the bottom or so-called gapside of the second pole tip region. As a result, there is a higher fluxdensity in the second pole tip region near the write gap layer at theABS and a lower flux density near the top of the second pole tip regionthat minimizes the magnitude of the flank field.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a conventional planar writehead with a top yoke comprised of a second pole tip region that has thesame thickness as the planar top yoke.

FIG. 2 is a top-down view of a conventional planar write head thatdepicts the shape of the planar top yoke and its relationship to the ABSand underlying coil layer.

FIG. 3 is a cross-sectional view from ABS that shows the second poletip, first pole tip, and write gap layer of the prior art planar writehead depicted in FIG. 1.

FIG. 4 is an enlarged view of pole tip regions in FIG. 1 that indicatesa large flank field near the second pole tip in addition to the gapfield used for recording.

FIG. 5 is a cross-sectional view of a write head with a planar top yokethat has a second pole tip region which forms a step near the ABSaccording to the present invention.

FIG. 6 is a cross-sectional view from the ABS of the write headstructure in FIG. 5 that depicts a second pole tip region with a smallerthickness than the backside region of the top yoke.

FIG. 7 is a top-down view of the write head structure in FIG. 5 showingthe shape of the second pole tip region and backside region of the topyoke.

FIG. 8 is an enlarged view of the pole tip regions in FIG. 5 whichindicates a reduction in size of the flank field compared to the flankfield in FIG. 4.

FIG. 9 is a cross-sectional view of a write head with a planar top yokethat has two steps from the backside region toward the ABS according toa second embodiment of the present invention.

FIG. 10 is a cross-sectional view from the ABS of the write headstructure in FIG. 9 that depicts a smaller thickness in second pole tipregion than in two segments of a backside region.

FIG. 11 is a top-down view of the write head structure in FIG. 9 thatshows the shape of the second pole tip region and backside region.

FIG. 12 is an enlarged view of the pole tip regions in FIG. 9 whichindicates a reduction in size of the flank field relative to the flankfield in FIG. 4.

FIG. 13 a is a plot that shows flank field magnitude as a function ofdown track position for a conventional planar write head while FIG. 13 bis a plot that indicates a smaller flank field with the stepped top yokeof the present invention.

FIG. 14 is a plot that shows the ratio of flank field to gap field as afunction of the size of the recess in the step in the top yoke of thefirst embodiment.

FIG. 15 is a plot which shows the ratio of flank field to gap field vs.the ratio of the thickness of the second pole tip region to thethickness of the backside region according to the first embodiment ofthe present invention.

FIG. 16 is a plot which shows the ratio of flank field to gap field as afunction of the combined recessed length of the two steps in the topyoke of the second embodiment.

FIG. 17 is a plot that shows the ratio of flank field to gap field vs.the ratio of the thickness of the second pole tip region to thethickness of the backside region according to the second embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a planar write head with a top yoke that isdesigned to direct magnetic flux during a write operation toward the gapside of a thinner second pole tip region in order to minimize a flankfield. The drawings are provided by way of example and are not intendedto limit the scope of the invention. Additionally, the figures are notnecessarily drawn to scale and the relative sizes of the variouselements may be different than in an actual write head.

A first embodiment is set forth in FIGS. 5-8 in which a key feature is aplanar top yoke comprised of a backside region and a second pole tipregion that forms a single step near the ABS. Referring to FIG. 5, aplanar write head 20 is shown that is part of a magnetic disk drive.Typically, the write head 20 is held by an arm (not shown) and issuspended over a rotatable magnetic disk on an air bearing surface (ABS)when writing a data track. It is important that during a writingoperation the write head does not erase adjacent data tracks. Accordingto the present invention, the shape of the write head is designed tominimize a flank field to prevent unwanted erasures.

The write head 20 is comprised of a first pole piece or bottom yoke 22that is formed on a substrate 21. In one embodiment, the substrate 21 isa non-magnetic material such as ceramic. Optionally, the write head maybe part of a merged head design in which the bottom yoke 22 also servesas the top layer in a read head (not shown). The bottom yoke isconnected to a second pole piece or top yoke 23 through a back gapregion 24. The length of the top yoke 23 from the ABS to the back gapregion is about 5 to 25 microns. The bottom yoke 22, top yoke 23, andback gap region 24 may be comprised of a ferromagnetic material such asNiFe or permalloy or may be a material with a high magnetic moment suchas CoNiFe, FeCo, or FeCoN. The bottom yoke 22 has a pedestal 25 with ashort throat region 26 and a first pole tip 27 which is the surface thatis formed along the ABS.

The planar top yoke 23 has a narrow front section 32 a and a second poletip region 32 b which have a combined length d₃ of about 1 to 3 micronsfrom the ABS toward the back gap region 24. A key feature of the presentinvention is that the second pole tip region 32 b which terminates atthe second pole tip 33 along the ABS is thinner than the front section32 a and forms a step down from the front section toward the write gaplayer 34. The front section 32 a, second pole tip region 32 b, andremainder of the top yoke 23 form a single piece. The second pole tipregion 32 b and throat region 26 are separated by a write gap layer 34having a thickness of about 0.08 to 0.14 microns which extends from theABS to a distance x of about 0.4 to 1.2 microns toward the back gapregion 24. Typically, the write gap layer 34 is comprised of anon-magnetic material such as Al₂O₃, silicon oxide, NiCu, Ru, or Pd. Itis understood that the second pole tip region 32 b and pedestal 25 arecomprised of the same material as in the top yoke 23 and bottom yoke 22.

In one embodiment, there is a cavity formed between the bottom yoke 22and top yoke 23 that extends from the short throat region 26 to behindthe back gap region 24. There is a dielectric layer 29 formed on thebottom yoke 22 which fills the cavity and has a top surface that iscoplanar with the write gap layer 34. Alternatively, there may be morethan one dielectric layer in the cavity. Within the dielectric layer 29is a coil layer 30 that is wrapped around the back gap region 24.Optionally, more than one coil layer may be employed. The dielectriclayer 29 is typically comprised of alumina, silicon oxide, siliconnitride, or a resin. The coil layer 30 includes a plurality of coilswhich are generally comprised of Cu or Au. An overcoat layer 35 isformed on the top yoke 23 and back gap region 24 and is preferably adielectric layer comprised of alumina or silicon oxide.

Referring to FIG. 6, a cross-sectional view of the write head 20 fromthe plane 36-36 in FIG. 5 is depicted. The second pole tip region 32 bhas a width w₂ of about 0.1 to 0.25 microns and a thickness t₁. Thefront section 32 a of the top yoke is recessed behind the second poletip region 32 b and has a thickness (t₁+t₂), and a width that istypically larger than w₂. Moreover, the width of the front section 32 atypically increases with increasing distance from the ABS. The thicknesst₁ is preferably in the range of about 0.4 to 1.2 microns and thethickness t₂ is preferably about 0.4 to 1.8 microns. The top surface ofthe front section 32 a is an extension of the top surface of the topyoke 23. The front section 32 a also has two sides (not shown) whichflare outward as the distance behind the ABS increases, a front end thatis adjacent to the back end of the second pole tip region 32 b, and aback end that is connected to the front end of the back section of thetop yoke 23. The bottoms of the first section 32 a and the second poletip region 32 b are coplanar with the write gap layer 34. The secondpole tip region 32 b has two sides that are perpendicular to the topsurface of the write gap layer 34, a back end, and a front end or secondpole tip 33 that is coplanar with the ABS.

An important aspect of the present invention is that the second pole tipregion 32 b is thinner than the front section 32 a. In particular, thetop of the second pole tip region 32 b is stepped down from the top ofthe front section 32 a so that a step is formed from the top yoke 23toward the ABS. In a preferred embodiment, the width w₂ of the secondpole tip region 32 b is equal to the width w₃ of the write gap layer 34,pedestal 25, and the first pole tip 27.

A top-down view of the top yoke 23 portion of the write head structure20 is shown in FIG. 7. Note that the front section 32 a is narrower thanthe larger back section 28. The front end of the front section that isadjacent to the second pole tip region 32 b has a smaller width than theback end which is connected to the back section 28 at a distance d₃ fromthe ABS.

Referring to FIG. 8, an enlarged view of the write head 20 near the ABSshows that the second pole tip region 32 b extends from the ABS to thefront section 32 a which is a distance d₄ of about 0.2 to 2 microns andpreferably about 0.3 to 1 microns. In other words, the step in the topyoke 23 extends a distance d₄ from the ABS toward the back gap region.When a current is applied to the coil layer, a magnetic flux 37 isgenerated in the top yoke 23 that passes through the front section 32 aand is directed toward the bottom (gap side) of the second pole tipregion 32 b and through the second pole tip 33. In so doing, a weakerflux density is formed near the top of the second pole tip region 32 b.As a result, the flank field 38 is significantly less than observed inprior art planar writers such as illustrated in FIGS. 1-4. The gap fieldis defined as the flux 37 which passes from the second pole tip 33through the intended magnetic recording track (not shown) adjacent tothe ABS. The flux 37 then passes from the recording track through thefirst pole tip 27 and into the pedestal 25. The thickness (t1+t2) of thefront section 32 a and top yoke 23 may be adjusted upward to increasethe gap field while maintaining the flank field 38 at an acceptable lowlevel.

One advantage of implementing the first embodiment of the presentinvention is illustrated in FIGS. 13 a-13 b in which the flank field 37is estimated as the maximum in-plane field at the magnetic disk surfaceat each down track position from the write head for a conventional head(curve 50) and for the write head with a stepped top yoke (curve 51).The results represented by curve 51 were generated with a t₁ thicknessof 0.7 microns, a t₂ thickness of 0.8 microns, and a d₄ distance of 0.6microns. The starting position at 0 microns in FIGS. 13 a, 13 b isdefined as the bottom of the second pole tip region at the ABS where thesecond pole tip meets the write gap layer. Increasing x-values representdown track positions progressively farther away from the startingposition. The write head of the present invention generates a smallerflank field, especially at down-track positions of greater than about0.3 microns. Note the rapid drop in flank field intensity (oersteds) forcurve 51 between the 0.3 and 1 micron down track positions. As mentionedpreviously, another advantage of the present invention is that a stronggap field can be achieved while keeping the flank field at a lowintensity that avoids track erasure.

The influence of the size of the recess d₄ on the ratio of flank fieldto gap field has been characterized and is illustrated in FIG. 14. Aconventional planar write head where the recess is 0 microns has a flankfield/gap field ratio of about 28%. The inventor has found that theflank field/gap field ratio is decreased to about 20% or less byintroducing a recess of 0.3 to 1 microns. However, a recess as small as0.2 microns or as large as 2 microns also offers some benefit.

Referring to FIG. 15, the present invention has been furthercharacterized by determining the effect of the step height t₁ as shownin FIG. 6 on the flank field/gap field ratio. The values on the x-axisrepresent the ratio t₁/(t₁+t₂) and indicate the largest reduction inflank field occurs when the thickness ratio is between 0.3 to 0.7. Theresults shown in FIG. 15 were generated with a t₁ thickness of 0.7microns, a t₂ thickness of 0.8 microns, and a d₄ distance of 0.6microns.

Those skilled in the art will appreciate that a step in the top yoke ofthe present invention may be readily constructed by conventionalmethods. For example, a first yoke layer with a thickness t₁ may beformed on the dielectric layer 29 by conventional means. Then a secondtop yoke layer with a thickness t₂ is fabricated on the first top yokelayer by a process sequence involving deposition, patterning, ionetching, and trim milling methods known to those skilled in the art. Thesecond top yoke layer is recessed from the ABS to form a first step.

The present invention also anticipates a write head with a planar topyoke that has a plurality of steps near the ABS. In the exemplary secondembodiment depicted in FIGS. 9-12, the top yoke has a second pole tipregion that represents one step and an adjacent segment in the frontsection of the top yoke that represents a second step.

Referring to FIG. 9, the write head 20 is comprised of the samecomponents as described in the first embodiment. The write head 20 maybe part of a merged head design in which the bottom yoke 22 also servesas the top layer in a read head (not shown). Alternatively, the bottomyoke 22 may be formed on a non-magnetic substrate 21 such as a ceramic.The planar top yoke 23 has been modified to include two steps. There isa second pole tip region 40 c and an adjacent front section of the topyoke 23 comprised of two segments 40 a, 40 b. The combined length d₅ ofthe second pole tip region 40 c and front section is the distance fromthe ABS to the back end of the segment 40 a.

The first segment 40 a in the front section is coplanar with the largerback section of the top yoke 23. The second segment 40 b in the frontsection forms a step down from the first segment 40 a toward the ABS andthe second pole tip region 40 c forms a step down from the secondsegment toward the ABS. The first segment 40 a, second segment 40 b, andsecond pole tip region 40 c together with the top yoke 23 form a singlepiece.

Referring to FIG. 10, a cross-sectional view of the write head 20 fromthe plane 41-41 in FIG. 9 is depicted. The first segment 40 a in thefront section of the top yoke is recessed behind the second segment 40 band has a thickness (t₃+t₄+t₅) and a width that is typically larger thanthe width w₂. Note that the sides of the first segment 40 a, secondsegment 40 b, and second pole tip region 40 c are perpendicular to aplane that is formed by the interface of the overcoat layer 35 anddielectric layer 29 and contains the top surface of the write gap layer34. Furthermore, the bottom of the first segment 40 a, second segment 40b, and second pole tip region 40 c are coplanar with the top surface ofthe write gap layer 34. The first segment 40 a has a back end that isconnected to the front end of the back section in the top yoke and afront end adjacent to the back end of the second segment 40 b. Thesecond segment 40 b has a width greater than w₂, a thickness (t₃+t₄), aback end, and a front end that is adjacent to the back end of the secondpole tip region 40 c. The second pole tip region 40 c has a width w₂ ofabout 0.1 to 0.25 microns, a thickness t₃, a back end, and a front endor second pole tip 33 that is coplanar with the ABS.

Preferably, the thickness t₃ is about 0.4 to 1.2 microns, thickness t₄is about 0.2 to 1.4 microns, and thickness t₅ is about 0.2 to 1.4microns. An important aspect of the present invention is that the secondpole tip region 40 c is thinner than the second segment 40 b which inturn is thinner than the first segment 40 a. In particular, the top ofthe second segment 40 b is stepped down from the top of the firstsegment 40 a and the top of the second pole tip region 40 c is steppeddown from the top of the second segment. The preferred ratio oft₃/(t₃+t₄+t₅) is from 0.2 to 0.6 and the preferred ratio oft₄/(t₃+t₄+t₅) is from 0.2 to 0.6. In a preferred embodiment, the widthw₂ of the second pole tip region 40 c is equivalent to the width w₃ ofthe write gap layer 34, pedestal 25, and the first pole tip 27.

Referring to FIG. 11, a top-down view of the top yoke 23 portion of thewrite head structure 20 is shown. There is a larger back section 28connected to the back end of the first segment 40 a of the front sectionof the top yoke at a distance d₅ from the ABS. The front end of thesecond segment 40 b that is adjacent to the second pole tip region 40 chas a smaller width than the front end of the first segment 40 a.

Referring to FIG. 12, an enlarged view of the write head 20 near the ABSshows that the second pole tip region 40 c extends from the ABS to thefront end of the second segment 40 b which is a distance d₇ of about 0.2to 1.5 microns. The second segment 40 b extends from the back end of thesecond pole tip region 40 c to the front end of the first segment 40 awhich is a distance d₆ of about 0.2 to 1.5 microns. In other words, thefirst step down from the top yoke 23 is comprised of the second segment40 b which has a back end that is recessed by the distance (d₆+d₇) fromthe ABS. The second step down from the top yoke 23 is comprised of thesecond pole tip region 40 c which extends a distance d₇ from the ABS.

When a current is applied to the coil layer (not shown), a flux 37 isgenerated in the top yoke 23 that passes through the first segment 40 aand is directed toward the bottom of the second segment 40 b (gap side).Similarly, the flux 37 that passes through the second segment 40 b isdirected toward the bottom (gap side) of the second pole tip region 40 cand through the second pole tip 33. In so doing, a weaker flux densityis formed near the top of the second pole tip region 40 c near the ABS.As a result, the flank field 38 is significantly less than observed inprior art planar writers such as illustrated in FIGS. 1-4. The flux 37passes from the recording track through the first pole tip 27 and intothe pedestal 25. This design enables the thickness (t₃+t₄+t₅) of thefirst segment 40 a and top yoke 23 to be adjusted upward to increase thegap field while maintaining the flank field 38 at an acceptable lowlevel.

The same advantages are achieved in the second embodiment as describedfor the first embodiment. For instance, the flank field observed for atwo stepped yoke as represented by curve 51 in FIG. 13 b is decreasedsignificantly at down-track positions compared with a flank field in aconventional planar writer (FIG. 13 a). Thus, unwanted erasure ofadjacent data tracks is prevented. Furthermore, a high gap field may begenerated while controlling the flank field at a low level.

The influence of the size (d₆+d₇) of the recess on the ratio of flankfield to gap field has been characterized and is illustrated in FIG. 16.A conventional planar write head where the recess is 0 microns has aflank field/gap field ratio of about 28%. The inventor has found thatthe flank field/gap field ratio is decreased to about 20% or less byintroducing two steps that are recessed by the distances d₇ and (d₆+d₇)from the ABS. The results shown in FIG. 16 were generated with a t₃ 0.7microns, a t₄ thickness of 0.5 microns, and a t₅ thickness of 0.5microns.

Referring to FIG. 17, the present invention has been furthercharacterized by determining the effect of the step thicknesses t₃, t₄,and t₅ depicted in FIG. 10 on the flank field/gap field ratio. Thevalues on the x-axis represent the ratio t₃/(t₃+t₄+t₅) and indicate thelargest reduction in flank field occurs when the thickness ratio isbetween about 0.2 to 0.4. The results shown in FIG. 17 were generatedwith a d₆ distance of 0.4 microns, and a d₇ distance of 0.6 microns.

Those skilled in the art will appreciate that one or more steps in thetop yoke of the present invention may be readily constructed byconventional methods. For example, a first yoke layer with a thicknesst₃ may be formed on the dielectric layer 29 by conventional means. Thena second top yoke layer with a thickness t₄ is fabricated on the firsttop yoke layer by a process sequence involving deposition, patterning,ion etching, and trim milling methods known to those skilled in the art.The second top yoke layer is recessed from the ABS to form a first step.Likewise, a third top yoke layer with a thickness t₅ may be formed onthe second top yoke layer with a similar process sequence involvingdeposition, patterning, ion etching, and trim milling steps. The thirdtop yoke layer has a larger recess from the ABS than the second top yokelayer and forms a second step.

While this invention has been particularly shown and described withreference to, the preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade without departing from the spirit and scope of this invention.

1. A method of forming a magnetic write head, comprising: (a) forming abottom yoke having a pedestal with a first pole tip and a short throatregion that is formed along an air bearing surface (ABS), said shortthroat region has a thickness, and a first length perpendicular to theABS; (b) forming a write gap layer above said pedestal; and (c) forminga planar top yoke connected to said bottom yoke through a back gapregion, said planar top yoke has a second pole tip region on said writegap layer and a front section that has a front end and a first thicknesswherein said front end is attached to a back end of said second pole tipregion and wherein said second pole tip region has a second thicknessless than said first thickness and the thickness of the short throatregion, a width, a second length perpendicular to the ABS and equal tosaid first length, and a front surface which is a second pole tip formedalong the ABS.
 2. The method of claim 1 wherein the length of saidsecond pole tip region is the distance from the ABS to the front end ofsaid front section which is about 0.2 to 2 microns.
 3. The method ofclaim 1 wherein the distance from the ABS to the back end of said frontsection is about 1 to 3 microns and represents the combined length ofthe second pole tip region and front section.
 4. The method of claim 1wherein the first thickness is about 0.8 to 3 microns and the secondthickness is about 0.4 to 1.2 microns and the ratio of said secondthickness to said first thickness is from about 0.3 to 0.7.
 5. Themethod of claim 1 wherein the width of said second pole tip region isabout 0.1 to 0.25 microns and wherein said write gap layer and saidfirst pole tip have a width that is equal to the width of said secondpole tip region.
 6. The method of claim 1 wherein the top yoke, secondpole tip region, and bottom yoke are comprised of NiFe, CoNiFe, FeCo, orFeCoN.
 7. The method of claim 1 further comprised of forming an overcoatinsulating layer on said planar top yoke, a dielectric layer betweensaid planar top yoke and said bottom yoke, and a coil layer within saiddielectric layer.
 8. The method of claim 1 wherein the distance from theABS to the back gap region is about 5 to 25 microns.
 9. The method ofclaim 1 wherein said planar top yoke has a bottom that is coplanar withsaid write gap layer.
 10. The method of claim 1 wherein said write gaplayer extends a distance of about 0.4 to 1.2 microns from said ABStoward said back gap region.
 11. A method of forming a magnetic writehead, comprising: (a) forming a bottom yoke having a pedestal with afirst pole tip that is formed along an air bearing surface (ABS); (b)forming a write gap layer above said pedestal; and (c) forming a planartop yoke connected to said bottom yoke through a back gap region, saidplanar top yoke is comprised of: (1) a back section that has a firstthickness and a front end attached to the back end of a front section;(2) a front section comprised of a first segment having a firstthickness, a length, front and back ends wherein the back end isattached to the front end of the back section, and a second segmenthaving a second thickness less than said first thickness, a length, andfront and back ends wherein the back end is adjacent to the front end ofsaid first segment and the front end is adjacent to the back end of asecond pole tip region; and (3) a second pole tip region having a thirdthickness less than said second thickness, a width, a length, and frontand back ends wherein the front end is a second pole tip formed alongsaid ABS.
 12. The method of claim 11 wherein the combined lengths ofsaid second segment and second pole tip region are equal to the distancefrom the ABS to the front end of the first segment which is about 0.4 to3 microns.
 13. The method of claim 11 wherein the length of the secondpole tip region is the distance from the ABS to the front end of thesecond segment which is about 0.2 to 1.5 microns.
 14. The method ofclaim 11 wherein the first thickness is about 0.8 to 4 microns, thesecond thickness is about 0.6 to 2.6 microns, the third thickness isabout 0.4 to 1.2 microns, and the ratio of said third thickness to saidfirst thickness is from about 0.2 to 0.6.
 15. The method of claim 11wherein said width of the second pole tip region is about 0.1 to 0.25microns.
 16. The method of claim 11 wherein said write gap layer extendsa distance of about 0.4 to 1.2 microns from the ABS toward the back gapregion.
 17. The method of claim 11 wherein the top yoke, second pole tipregion, and bottom yoke are comprised of NiFe, CoNiFe, FeCo, or FeCoN.18. The method of claim 11 wherein the width of said second pole tipregion is the same as the width of the write gap layer, first pole tip,and pedestal.
 19. The method of claim 11 further comprised of anovercoat insulating layer which is formed on said planar top yoke, adielectric layer formed between said planar top yoke and said bottomyoke, and a coil layer formed within said dielectric layer.
 20. Themethod of claim 11 wherein the distance from the ABS to the back gapregion is about 5 to 25 microns.